1. Technical Field
The present disclosure relates to performance tests of a system compensating trembling movements of which the human body and in particular the hands are afflicted, during operations benefiting from an object being held as still as possible or with a precision as high as possible.
2. Description of the Related Art
Certain image capture apparatus, such as photography apparatus and digital cameras, are equipped with such a system to compensate for trembling movements during the holding of the apparatus, and thus improve the sharpness of blurry images during the capture of an image. These trembling movements are that much greater when the apparatus is light and can be held with a single hand.
Human trembling movements consist of involuntary vibratory movements that are cumulated with voluntary movements. These vibratory movements generally present amplitudes of several tens of millimeters to several millimeters, and can comprise several harmonics from 0.1 Hz to 20 Hz, as well as presenting angular speeds of about 2°/s and/or linear speeds of about 2 mm/s.
Therefore, electromechanical image stabilization systems exist that comprise acceleration and rotational speed sensors to measure trembling movements, as well as actuators to compensate these movements by displacing optical elements or the image sensor of the image capture apparatus. Due to their higher prices and their large bulk, these systems are usually used with high-range and voluminous photo apparatus, such as reflex cameras.
For lower-range apparatus such as “compact” photographic apparatus and those installed on mobile telephones, image stabilization algorithms have been devised that aim to correct the blurry effect in the captured images. This effect results from trembling movements while the apparatus was held. Certain image stabilization systems are based on a detection of the trembling movements. In some systems, the detection of trembling movements is done with the aid of sensors, and in other systems, it is done by the comparison of successive images. Based on the detected trembling movements, image stabilization algorithms apply a correction to the image that aims to limit or negate the blurry effect. Other image stabilization algorithms consist of using an image taken at the required speed and an image taken at a higher speed to produce a corrected image.
A need exists for a performance test of such image stabilization or correction systems, with the aim of development, characterization, and comparison of different existing image stabilization systems. To this end, these systems may be tested by several people. Nevertheless, such tests turn out to be insufficient due to the difficulty of selecting an adequately representative sample of people to obtain conclusive results. Another problem is test reproducibility, in particular to perform comparisons. Indeed, it is impossible for a person to reproduce exactly the same trembling movement, which is involuntary by nature.
Automated systems exist that allow the displacements and the spatial position of an object to be controlled. These systems turn out, in general, to be incapable of generating amplitude and frequency controlled vibrations with a sufficient precision to simulate, in a reproducible manner, human trembling movements, in particular due to a too high inertia and/or response time. In particular, these systems cannot generate frequency vibrations greater than 10 Hz, whereas a human tremble can reach a frequency of 20 Hz. These systems are also incapable of reproducing a vibratory movement combining several frequencies and amplitudes. Moreover, certain systems with an automated arm need to be within a secure enclosure, which is incompatible with the holding of an image capture apparatus that needs to be directed towards a scene in order to perform stabilization tests of the imaging system.
It may therefore be desirable to use a performance test device of an image stabilization system, in particular for an image capture apparatus, that is capable of reproducing one or more combined human trembling movements, with a sufficient precision of both frequency and amplitude.